Power transmission



April 24, 1951 A. M. LANE POWER TRANSMISSION Filed March 50, 1946 Mill INVENTOR. ALBERT M. LANE Patented Apr. 24, 1951 POWER TRANSMISSION Albert M. Lane, Detroit, Mich., assignor to Vickers Incorporated, Detroit, Mich., a. corporation of Michigan Application March 30, 1946, Serial No. 658,483

Claims. 1 I This invention relates to power transmissions, particularly to those of the type comprising two or more fluid pressure energy translating devices, one of which may function as a pump and another as a fluid motor.

This invention is particularly concerned with flow control devices and especially with those of the type comprising a compensating valve and throttle. Such controls are well known in the art, particularly as employed in transmission panels for machine tools as illustrated in Patent No. 2,267,177 to Twyman and Patent N 0. 2,303,946 to Miller.

Reciprocating, double-acting piston motors are generally employed in the art for operating machine tool tables. The operating fluid pressure and volume are maintained constant by the flow control device, andtherefore, to equalize the rate of travel of the motor piston and work table, it

has been the practice in the past to employ a '1 through rod for the piston. In other words, the piston rod extends in both directions from the piston to the opposite ends of the cylinder, thereby providing equal displacement for each end of the motor. By employing the well-known pressure-actuated compensating valve in combination with a throttle, the flow rate and table speed were accurately controlled and equalized in both directions.

It has been found desirable to increase the fluid flow rate during certain portions of the hydraulic transmission cycle. Such a condition is inherent when the hydraulic reciprocating motor is of the difierential-piston type and where the piston rod extends only from one side of the piston to the head of the cylinder.

In that case the displacement of the one side of the motor is greater than the other. It is evident that a constant flow rate through the combination throttle and compensating valve control will produce two different rates of work table travel in proportion to the motor piston displacements. If it is desirable to maintain equalized table travel in both directions, then the flow rate must vary with the displacement of the load device.

Therefore, the general object of this invention is to provide means for automatically modifying the operation of the combination throttle and compensating valve flow rate control.

Another object is to provide hydraulic means for varying the compensating valve operation only during a pre-determined portion of the operating cycle.

More specifically, an object of the invention all) 2 is to provide an increase or decrease in pressure fluid flow during a portion of the operating cycle in proportion to the displacement characteristics of a load device.

A further object is to provide auxiliary hydraulic means for modifying the compensating valve operation during the period of supplying a load device requiring such modified flow, said auxiliary means being provided with hydraulic operating fluid from the supply source only during that period.

The standard flow rate control, comprising a throttle in combination with a pressure-balanced, piston-actuated compensating valve, includes a spring of pre-determined tension establishing the calculated flow rate. One of the objects of this invention is to provide means for varying the compression of that spring for increasing or decreasing the calculated flow rate.

In accordance with the preferred form of the invention illustrated herein, it is also an object to provide a transmission system employing a differential-piston type of hydraulic motor for operating a machine tool work table at equal rates of travel in each direction.

A further object is to provide a compact control panel for housing the transmission controls.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing:

The single figure illustrates a diagrammatic view of a grinder table and control panel incorporating a preferred form of the present invention.

Referring now to the drawing, a pump l0 driven by a prime mover I 2 has a suction conduit I 4 through which fluid may be drawn from a tank IE to an operating pressure conduit l8. The conduit l8 extends to a chamber of a compensating valve 22 which is in a control panel 24 and is adapted to bypass fluid to tank it by a relief conduit 26 and a tank conduit 28 whenever a pre-determined pressure is exceeded in the chamber 20.

Operating pressure fluid flows from chamber 20 through a conduit 30 and throttle 32 to a port 34 of a reversing valve chamber 36. From port 34, operating fluid is directed around land 38 of a reversing valve 40 to a reciprocating motor 42 via port 44 and conduit 46 to a cylinder chamber 48 or via port 50 and conduit 52 to a cylinder chamber 54 of smaller displacement.

The motor 42 is provided with a piston 56 connected by a rod 58 to a table 66 by means of link 62.

Reversing valve 46 is hydraulically shifted and controlled by pilot valve 64. Dogs 66 and 68 attached to the table 66 are positioned to contact and shift arms I6 and I2, respectively, at the extreme right or left travel of the table 66. Arms I6 and I2 are fastened to shaft I4 which in turn carries a ball joint arm I6 for shifting pilot valve 64. Therefore, as illustrated, when the table 66 has reached its extreme travel to the right, dog 66 will contact arm I6 and shift pilot valve 64 to the left.

When the pilot valve 64 has been shifted to the left as illustrated in the drawing, pressure fluid is admitted to the righthand end of reversing valve 46 for shifting it to the left. The hydraulic fluid is communicated from chamber 26 to chamber I8 via conduit 86, ports 82 and 84, conduit 86, and check valve 88. Hydraulic pressure exerted against the right end of valve 46 will shift the valve against the pocketed pressure which is adapted to be metered out of the opposite end thereby controlling the rate of shifting valve 46.

The hydraulic fluid pocketed in chamber 96 is metered out or released as the reversing valve 46 is shifted to the left, by means of the conduit 92, needle valve 94, conduit 96, ports 98 and I66, and conduits I62, I64, and I66, to tank I6. Adjustable positive stops I68 and H6 are provided for limiting the travel of reversing valve 46.

When the table 66 and piston 56 reach their extreme left position, dog 68 will actuate arm ":2, thereby shifting pilot valve 64 to the right. Shifting of valve 64 to the right will direct pressure fluid from conduit 86 to chamber 96 at the left end of the reversing valve 46 via ports H2 and S8, conduit 96 and check valve I I4. Pressure fluid pocketed in chamber I8 at the right end of the reversing valve 46 will be metered out through needle valve II6, conduit 86, ports 84 and H8, conduits I62, I64, and I66 to tank I6.

During the travel of piston 56 to the left with the valve positioned as shown in the drawing, chamber 48 will be exhausted through conduit 46, ports 44, and I26, conduit I22, port I24, chamber I26, conduits 26 and 28 to tank I6. In the reverse direction, chamber 54 exhausts through conduit 52, ports 56 and I28, conduit I36, port I32, exhaust chamber I26, exhaust conduits 26 and 28 to tank I6.

The speed of table 66 is controlled by the pressure fluid flow rate through conduit 36 which in turn is controlled by the combination throttle 32 and compensating valve 22-. The valve 22 is pressure operated by the piston I34 in conjunction with the spring I36. The difference in pressure between chambers 26 and I38 on either side of the piston I34, in cooperation with spring I36, will control the opening and closing of valve 22. It will be noted that chamber 26 and the upper side of piston I34 are subject to the operating pressure ahead of the throttle 32, while chamber I38 and lower side of piston I34 are subject to the operating pressure beyond the throttle 32 and communicated thereo by conduit I46. A restriction I42 and pilot relief valve I44 are provided in conduit I46. A relief valve chamber I46 is connected to tank I6 by conduits I48, I56, and I66.

At the lower end of compensating valve 22 an auxiliary piston I52 is providedin'a cylinder I54 which is connected by a conduit I56 and port 4 44 to the operating conduit 46 of the larger motor cylinder chamber 48. A drain I58 for cylinder I54 above the piston I52 is provided in an auxiliary piston rod or stem I66. The drain i518 connects to an axial drain I62 in tho compensating valve 22 which in turn leads to tank conduits 26 and 28.

In operation, pressure-operating fluid is directed to chamber 54 of motor 42 from tank I6 via conduit I4, pump I6, conduit I8, chamber conduit 86, throttle 32, ports 34 and 56, and

conduit 52. The rate of travel of piston 56 and table 66 will depend upon the hydraulic flow rateor pressure drop through throttle 32.

The flow control device, comprising the compensating valve 22, throttle 32, conduit I46 and relief valve I44, provide a means for controlling the travel rate of the motor piston 56. The compensating valve piston I34 is of the doubleacting, pressure-balanced type wherein the upper face is subjected to the operating fluid pressure in chamber 26. The pressure in chamber I33 is communicated from a point beyond the throttle 32 through conduit I46. The compensating valve 22 shown in the drawing is of the relief type wherein excess pressure ahead of the throttle 32 is relieved through conduits 26 and 23 to tank I6.

fhe spring I36 of pre-determined compressive force urges the valve 22 into a closed position. Assuming equal piston areas, if the difference in fluid pressure between chamber 26 and chamber I38 was equal to the normal force of spring I56, the compensating valve 22 would be balanced in a closed position. If the fluid pressure ahead of the throttle in chamber 26 was greater than the pressure beyond the throttle in chamher I36 by-an amount greater than the force of spring I36, the valve 22- would open, thereby reducing the pressure in chamber 26 until the drop in pressure across the throttle became equal to the pre-determined force of the spring I36. Therefore, by maintaining a constant pressure drop across the throttle 32, the hydraulic flow rate in conduit 36 is controlled.

Uniform pressure operation is provided by means of the relief valve I44 which is connected to tank I6 via chamber I46 and conduits I48, and I66. When the fluid pressure beyond the throttle 32 becomes excessive, the relief'valve I44 will open to relieve the pressure in chamber I38 and permit the main valve 22 to open. The replenishing flow from conduit 36 to chamber I38 through conduit I46 is restricted at I42, whereby the unobstructed flow from chamber I38 to valve I44 is greater than the replenishing supply from conduit 36 through restriction I42.

As described abovepunder normal operation of the compensating valve 22 and throttle 32, the constant flow is dependent upon the drop in pressure through the throttle 32 which in turn is dependent upon the pre-determined compressive force of spring I36. 'To change thepressure drop and flow rate therefor, it is necessary to change the compression of spring I36. Hydraulically-operated piston I52 is adapted to risein cylinder I54 and'further compress spring I36. Consequently, when cylinder chamber 48, the larger of the two motor wcylinders, is under operating pressure communicated through port 44 and conduit '46, the piston :I52- is also subjected to operatingpressure through conduit I56 frorn'p'ort 44. In other words-tomainteiinequal travel rates of the piston 56 in each direction, the v larger chamber 48 would require a greater 5. flow rate to satisfy the increased displacement. Therefore,.the auxiliary piston I52 is connected to a source of operating pressure, such as at port 44, during that portion of the cycle in which an increase in flow rate is necessary.

The feature or" modifying the operation of the flow control through a portion of the cycle has been shown for a condition where increased flow rate is desired as, for example, where constant travel of a double-acting diiterential piston is necessary. Ihe conduit I58 may be connected to any portion of the circuit having a variation in pressure characteristics during the period oi required modiflcation'merely for the purpose of timing the change in rate. The same eilect may be accomplished by setting the control for maximum flow rate and then have the auxiliary piston operate to reduce the tension of spring 336 during the portion of the cycle a reduction in flow rate is desired. Various combinations of con trol and rate can be accomplished by merely having the auxiliary piston respond to a selected cyclic function or functions.

Although the auxiliary means and preferred method for modifying the flow rate has been illustrated and described as modifying the compensating valve operation, it may be linked to the throttle instead. In the latter case the auxiliary control could be made to vary the throttle directly or control a hydraulic conduit adapted to by-pass the throttle, or other ways of modifying the throttling action.

It will thus be seen that the present invention has provided a control for transmission systems having a normally constant flow rate but, at the same time, includes features for modifying the rate through any selected portion of the cycle of operation. This is accon plished by a pressure-actuated auxiliary piston adapted to modify the normal flow control rate and includes means for limiting the communi cation of actuating pressure to that portion of the operating cycle during which the desired modification is required.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimedis as follows:

l. A flow control valve for a hydraulic power transmission employing a pressure fluid source and a reversible fluid motor of the reciprocating difierentialpiston type, comprising a throttle and pressure actuated compensating valve controlled by fluid pressure ahead of and beyond the throttle for maintaining a constant fluid flow rate to the end of the motor having the smaller displacement, and auxiliary hydraulic means actuated by operating fluid pressure supplied to the end of the motor having the larger displacement for modifying the normal comp nsating valve operation and increasing the fluid flow rate to the larger displacement or" the motor during that portion of the motor cycle when the larger displacement end of the motor is supplied with pressure fluid.

2. A flow control valve for a hydraulic powe transmission employing a pressure fluid source and a reversible fluid motor of the reciprocating differential piston type, comprising a throttle and pressure actuated compensating valve con trolled by fluid pressure ahead of any beyond the throttle for maintaining a constant fluid flow rate to the end ofthe motor having the smaller displacement, and an auxiliary piston and a resilient link positioned between the compensat-. ingvalve and the auxiliary piston for modifying the compensating valve operation when the auxiliary piston is actuated by pressure fluid supplied to the larger displacement end of the motor for increasing the fluid flow rate to the end of the motor having the larger displacement.

3. A flow control device for a hydraulic transmission including a throttle in combination with a pressure actuated compensating valve for maintaining a constant pressure drop across the throttle, and auxiliary pressure actuated means for modifying the action of the compensating valve during a part of the cycle and changing the flow rate through the throttle, said auxiliary means being actuated by fluid pressure from that portion of the circuit in which the flow rate is to be changed during that part of the cycle. 4. A flow control device for a hydraulic transmission including a throttle in combination with a pressure actuated compensating valve, including a piston exposed to pressure ahead of and beyond said throttle for maintaining a constant pressure drop across the throttle, and pressure actuated means for modifying the operation'of the compensating valve including an auxiliary piston linked to the compensating valve, and auxiliary pressure fluid conduits connecting the auxiliary piston to a pressure fluid operated element of the transmission requiring a modified flow of pressure fluid during a part of the work cycle.

5. A flow control device comprising a throttle in combination with a pressure balanced piston type compensating valve, one side of the valve piston being subject to fluid pressure beyond the throttle for increasing the flow rate, the other side of the balanced piston being subject to fluid pressure ahead of the throttle, and tending to decrease the flow rate, a spring providing a predetermined compression iorce adapted to assist the pressure fluid from beyond the throttle thereby tending to upset the pressure balance and produce a pre-determined pressure drop across the throttle in proportion to the spring compression, and auxiliary pressure means for automatically changing the spring compression and modifying the pressure drop across the throttle thereby varying the hydraulic fluid flow rate through the control.

6. A flow control device for a hydraulic transmission comprising a throttle in combination with a pressure balanced piston type compensating valve, one side or" the valve piston being subject to fluid pressure beyond the throttle for increasing the flow rate, the other side of the balanced piston being subject to fluid pressure ahead of the throttle, and tending to decrease the flow rate, a spring providing a pre-determined compression force adapted to assist the pressure fluid from beyond the throttle thereby tending to upset the pressure balance and produce a pre-determined pressure drop across the throttle in pro-.

portion to the spring compression, an auxiliary piston adapted to change the spring compression and modify the pressure drop across the throttle during a certain portion of the cycle, the auxiliary piston being connected to and actuated by fluid pressure from a part of the transmission circuit subjected to operating pressure during that certain portion of the cycle.

7 A hydraulic transmission comprising a source of operating pressurefluid, a hydraulic motor of the reciprocating double acting differential pistontype,

a flow control device including athrottle in combination with a pressure actuated compensating valve controlled by fluid pressure ahead of and beyond the throttle for maintaining a constant pressure drop and fluid flow rate through the throttle when normally supplying operating pressure fluid to the motor, and an auxiliary hydraulic means linked to the compensating valve for modifying the flow rate in proportion to the displacement of the motor cylinder being filled thereby maintaining an equal rate of travel of the motor piston in both directions regardless of displacement.

8. .A hydraulic transmission comprising a source of operating pressure fluid, a hydraulic motor of the reciprocating double acting .difierential piston type, a flow control device including a throttle in combination with a pressure actuated compensating valve controlled by fluid pressure ahead of and beyond the throttle .for maintaining a constant pressure drop and fluid flow rate through the throttle when normally supplying operating pressure fluid to the motor, and means for equalizing the rate of travel of the hydraulic motor piston in both directions includ ing a hydraulically operated piston for automatically modifying the operation of the compensating valve during a part of the motor operating cycle.

9. Ahydraulic transmission comprising a source of operating pressure fluid, a hydraulic motor of the reciprocatin double acting differential piston type, a flow control device including a throttle in combination with a pressure actuated compensating valve controlled by fluid pressure ahead of and beyond the throttle for maintaining a constant pressure drop and fluid flow rate through the throttle When normally supplying operating pressure fluid to the motor, and an auxiliary hydraulic means linked to the compensating valve for modifying the flow rate in proportion to the displacement of the motor cylinder being filled thereby maintaining an equal rate of travel of the motor piston in both directions regardless of displacement, the auxiliary means being actuated and controlled by operating pressure during that portion of the cycle in which the flow rate is modified.

10. A hydraulic transmission comprising a source of operating pressure fluid, a hydraulic'motor of the reciprocating double acting differential piston type, a flow control device including a throttle incombination with a pressure actuated compensating valve controlled by fluid pressure ahead of and beyond the throttle for maintaining a constant pressure drop and fluid flow rate through the throttle when normally supplying operating pressure fluid to the motor, and means for equalizing the rate of travel of the hydraulic motor piston in both directions including a hydraulically operated piston for automatically modifying the operation of the compensating valve during a part of the motor operating cycle, and hydraulic conduitsconnecting the piston to a part of the transmission circuit carrying operating pressure during the modified portion of the motor cycle.

11. A flow control device for a hydraulic transmission including a throttl in combination with a pressure actuated compensating valve for maintaining a constant pressure drop across the throttle, and auxiliary pressure actuated means for modifying the action of the flow control device during a part of the cycle and changing the flow rate. through the throttle, said auxiliary means 8 being actuated by fluid pressure from that portion of the circuit in which the flow rate is to be changed during that part of the cycle.

:12, A flow control device comprising a throttle in combination with a pressure balanced piston type compensating valve, one side of the valve piston being subject to fluid pressure beyond the throttle for increasin the flow rate, the other side of the balanced piston being subject to fluid pressure ahead of the throttle, and tending to decrease the flow rate, a spring providing a predetermined compression force adapted to assist the pressure fluid from beyond the throttle thereby tending to upset the pressure balance and produce a pre-determined pressure drop across the throttle in proportion to the spring compression, and auxiliary pressure means for automatically modifying the operation of the flow control device during a portion of the cycle requiring an abnormal demand.

13. A flow control device for a hydraulic transmission having a pressure fluid source and a pressure fluid operated element requiring a regulated modified flow rate and comprising in combination a first throttle valve and a second throttle valve in series, the first of which includes first operating means responsive to the pressures ahead of and beyond the second throttle for maintaining a constant pressure drop across the second throttle, a second pressure responsive operating means operatively connected to one of said throttles for modifying the pressure drop across the second throttle, and at least one hydraulic conduit adapted to be connected to the fluid operated element requiring the modified flow rate and connected to the second operating means for supplying pressure fluid thereto for operating the same and thereby modifying the flow rate in said conduit leading to the fluid operated element.

14. A flow control device for a hydraulic transmission having a pressure fluid source and a pressure fluid operated element requiring a regulated modified flow rate and comprising in combination a throttle and a pressure compensating valve in series, the compensating valve including operating means responsive to the pressures ahead of and beyond the throttle for maintaining a constant pressure drop across the throttle, a second pressure responsive operating means connected to the compensating valve for causing the latter to modify the pressure drop across the throttle, and at least one hydraulic conduit adapted to be connected to the fluid operated element requiring the modified flow rate and connected to the second operating means for supplyin pressure fluid thereto and causing the compensating valve to modify the pressure drop across the throttl and thereby modify the flow rate in said conduit leading to the fluid operated element.

15. .A flow control device for a hydraulic transmission having a pressure fluid source and a pressure fluid operated element requiring a regulated modified flow rate and comprising in combination a throttle and a pressure compensating valve in series, the compensating valve including operating means responsive to the pressures ahead of and beyond the throttl for maintaining a constant pressure drop across the throttle, a second pressure responsive operating means connected to the compensating valve for causing the latter to modify the pressure drop across the throttle, and at least one hydraulic conduit for supplying pressure fluid to the second operating means and adapted to be connected to the pressure fluid source during that portion of the transmission cycle in which the pressure fluid operated element requires a modified flow rate.

ALBERT M. LANE.

REFERENCES CITED The following references are of record in the file of this patent:

Number 10 1 UNITED STATES PATENTS Name Date Vickers Dec. 21, 1937 Harrington Oct. 21, 1941 Miller Dec. 1, 1942 Linden et a1 Jan. 18, 1944 Welte Feb. 26, 1946 Peterson et a1 Aug. 26, 1947 

